JPH076169B2 - How to install and tension cable-stayed cables - Google Patents

Description

The present invention relates to a cable-stayed cable used in a cable-stayed bridge, which is constructed by inserting a cable-stayed cable composed of a large number of strands into a cable protection tube and erected to introduce tension. Concerning the cable tension method.

[Conventional technology]

As for the cable-stayed cable of the long cable-stayed bridge, many on-site cables composed of many strands (37 to 91 strands) (PC steel stranded wire) are used. The tension of this cable-stayed cable is originally 1
The basic method is a collective tension method in which all the strands that make up a cable-stayed cable are tensioned at the same time.

However, in order to tension the cable-stayed cables all together, a method such as supporting the protective tube of the cable-stayed cable with scaffolding support, or hanging it with a hanger wire and holding it in the air, and inserting a strand into it is possible. I had to erection.
However, it is inefficient to assemble the scaffolding support and to hang the hanger wire of large diameter on the long cable stayed bridge constructed by the overhanging method.Therefore, before inserting the strand, protect the protection tube with the above method. It was not common to hold and cable-stayed cables were not collectively tensioned.

As an alternative to the collective tension method, first insert a few of the many strands that make up one cable-strand cable into the protective tube to tension it and keep the protective tube in the air. Insert the remaining strands one by one and tighten each one, or insert all the remaining strands and then
The split tension method, in which each book is tense, was adopted.

In the split tension method, when the strand is tensioned, the main girder and the main tower are elastically deformed, and the tension of the previously tensioned strand changes. However, this amount of change is affected by Young's modulus of concrete and temperature change during tension work. Therefore, in the split tension system, the cable-stayed cable 1 at the time when the tension of all the strands constituting one diagonal member is completed.
When trying to grasp the tension as a book, this tension has to be calculated as a calculated value, so that there is a big drawback that the precision is poor because it includes an error due to the influence of the Young's modulus of concrete and the like.

[Object of the Invention]

The present invention has been made in view of the above problems. The purpose is to increase the accuracy of tension introduction and work efficiency by collectively tensioning the many strands that make up one cable-stayed cable without the need for scaffolding support for the installation of the cable-stayed cable. The purpose is to propose a method of erection and tension of a cable-stayed cable that can be achieved.

[Structure of Invention]

This cable-stayed cable is laid and tensioned by inserting the cable-stayed cable composed of a large number of strands into a cable protection tube and then tensioning it. Insert the tube into the tube and temporarily tension the leading strand to hold the cable protection tube in the air.In this state, insert the remaining many trailing strands into the cable protection tube and tighten them in a lump, then tension the leading strand. It is characterized by introducing a predetermined tension.

[Action]

With this method, many trailing strands are collectively tensioned by the center hole jack while the protective tube and trailing strands are held in the air by about 1 to 3 leading strands. Can read,
Except for various factors that cause errors, highly accurate tension is possible and workability of erection and tension is improved. After tensioning a large number of strands at once, the preceding strand is re-tensioned so as to have a predetermined tension.
Since the number of strands is less than the number of trailing strands, the influence on the trailing strands is extremely small and does not cause a problem in tension management.

〔Example〕

Hereinafter, the method of constructing and tensioning the cable-stayed cable of the embodiment will be described in the order of steps with reference to the drawings.

Figure 1 shows the main tower 1 and main girder 2 of the cable-stayed bridge where the cable-stayed cable is erected. Prior to the cable installation, a spiral spacer wire is inserted into the cable protection tube 3 (unit made of polyethylene and having a predetermined length) on the main girder 2 and welded to each other to obtain the cable installation length. The pilot wire 4 is inserted into the protective tube 3.

In FIG. 2, a hoisting jig 5 is attached to the tip of the protective tube 3 and hoisted by a tower crane 6 attached to the main tower. Subsequently, in FIG. 3, the protection tube 3 is temporarily fixed to the main tower 1 by using the tip jig 5 and the pilot wire 4. At this time, the lower end of the pilot wire 4 is fixed to the main girder. In FIG. 3, 8 is a cable fixing hole provided in the main tower, 9
Is a lever block.

In Fig. 4, two of the 61 strands (15mm steel stranded wire) forming the cable-stayed cable are replaced by the preceding strand 10-1.
After that, the push-in machine 11 pushes and inserts the protective tube 3 temporarily fixed from the upper end. In FIG. 5, this strand 10-1 is fixed at its lower end to a cable fixing member installed on the main girder 2 and temporarily tensioned by a single-strand jack 12 arranged at the upper end position. The tension of temporary tension is 9.8 (t ・
f), 4.9 (t · f) per strand. The cable sag (the maximum slack distance of the strand with respect to the straight line connecting both ends of the strand) was 500 mm.

In FIG. 6, the pilot wire 4 is removed, and the protection tube 3 is held in the air between the main tower 1 and the main girder 2 by the preceding strand 10-1. In FIG. 7, 59 strands 10-2 to be succeeding by inserting the fixing holes 8 of the main tower 1 into the protective tube 3 held in the air are pushed and inserted by the pushing machine 11. After insertion, the tension applied to the preceding strand 10-1 is 2
5.9 (tf) per strand, 12.95 (tf),
The cable sag was 2.031 mm.

Marking for tension control is made on the following strand 10-2 inserted in Fig. 8 and the lower end of the main girder 2
It is fixed to the cable fixing body installed in. All of the 59 subsequent strands 10-2 are collectively tensioned by the center hole jack 13 to introduce a predetermined tension, and the upper end is fixed to the fixing hole 8 portion of the main tower 1. At this time, the tension of the trailing strand 10-2 is 485.52 (t · f), 8.2 (t · f) per strand, and the tension applied to the preceding strand 10-1 is 8.0 (t · f), 4.0 (per strand). tf) and the cable sag was 99 mm.

Then, the preceding strand 10-1 is re-tensioned with a single-strand jack to introduce a predetermined tension force, and then fixed to the fixing hole 8 portion. Trailing strand at this time
Tensile force of 10-2 is 16.4 (tf), and 8.2 (t
f) The tension applied to the trailing strand 10-2 is 485.48 (t.
f) It is 8.2 (tf) per cable, and cable sag is 9
It was 7 mm. In the final process, the preceding strand was re-tensioned, but the tension of the trailing strand after it was collectively tightened was 485.52 (t
It was a slight change from f) to 485.48 (t · f), which was a negligible value for one strand.

〔The invention's effect〕

 The present invention is as described above, and has the following effects.

Since this method directly measures the tensions of the majority of the strands constituting one cable-strand cable directly, it is possible to introduce the tension force with higher accuracy than the conventional split tension method.

The conventional split tension method required about two days for cable tension, but this collective tension method required about half a day for tension, resulting in a significant improvement in work efficiency.

Since it does not require scaffolding support or hanger cables, and can be applied to cable-stayed bridges with overhanging methods, it has a wide range of applications and can streamline the process.

[Brief description of drawings]

FIGS. 1 to 8 are side views of a cable-stayed bridge showing the cable-stayed cable installation and tensioning method in the order of steps, and FIGS. 1, 2, 3, 4, and 7 (b).
Is an enlarged view of the upper end of the cable protection tube, and FIG. 3 (c) is an enlarged view of the lower end of the cable protection tube. 1 …… Main tower, 2 …… Main girder, 3 …… Cable protection tube, 4 …… Pilot wire, 5 …… Hoisting jig, 6 …… Tower crane, 7 …… Winch, 8 …… Cable fixing hole, 9 …… Lever block, 10-1 …… Leading strand, 10-2 …… Trailing strand, 11 …… Pushing machine, 12 …… Single strand jack, 13 …… Center hole jack

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Kanazawa 13-13 Arakicho, Shinjuku-ku, Tokyo Sumitomo Construction Co., Ltd. (56) References 142108 (JP, A) Japanese Patent Publication 1-15646 (JP, B2)

Claims (1)

[Claims] 1. A method of inserting a cable-stayed cable of a cable-stayed bridge composed of a large number of strands into a cable protection tube in which the cable is laid and tensioning the same, wherein several of the plurality of strands are used as preceding strands in the cable protection tube. Insert and temporarily tension the leading strand to hold the cable protection tube in the air,
A method of constructing and tensioning a cable-stayed cable, characterized in that the remaining large number of trailing strands are inserted into the cable protection tube in this state and tensioned collectively, and then the preceding strand is tensioned to introduce a predetermined tension.